Electroluminescent devices which are known include a two-layer structure in which an organic fluophor thin film 3 and an organic hole transport layer 4, respectively, composed of organic compounds and laminated on each other are disposed between a metal electrode 1, as a cathode, and a transparent electrode 2, as an anode, as shown in FIG. 2, and a three-layer structure in which an organic electron transport layer 5, an organic fluophor thin film 3, and an organic hole transport layer 4 laminated one on one are disposed between a metal electrode 1 and a transparent electrode 2, as shown in FIG. 3. The organic hole transport layer 4 has the double function of making holes injected easily from the anode and blocking electrons. The organic electron transport layer 5 has the function of making it easy for electrons to be injected from the cathode.
In this type of electroluminescent device, a glass substrate 6 is disposed outside of the transparent electrode 2. Excitons are produced by recombination of electrons injected from the metal electrode 1 and holes injected from the transparent electrode 2, so that light is emitted as radiation and inactivation of the excitons and discharged externally through the transparent electrode 2 and the glass substrate 6.
In the conventional electroluminescent devices configured as described above, the lifetime of the device depends on the chemical stability of the fluorescent substance, so that the chemical stability changes easily with the passage of time. Accordingly, a disadvantage arises in that the device deteriorates easily. Further, a disadvantage arises in that luminescent efficiency is too low to obtain luminescence with high brightness.